Only two EO's have every been overturned. One was Clinton's (Chamber of Commerce of the United States v. Reich)
The court ruled (in part) that the Clinton EO was unconstitutional because Clinton tried to re-write Labor Laws and not enforce labor laws.
Obama could be taken to court for the same reason, but he recently packed the 'DC Court of Appeals,' so it could be harder to reverse this action.
Congressional Recourse
If Congress does not like what the executive branch is doing, it has two main options. First, it may rewrite or amend a previous law, or spell it out in greater detail how the Executive Branch must act. Of course, the President has the right to veto the bill if he disagrees with it, so, in practice, a 2/3 majority if often required to override an Executive Order.
Congress is less likely to challenge EOs that deal with foreign policy, national defense, or the implementation and negotiation of treaties, as these are powers granted largely to the President by the Constitution. As the Commander-in-Chief of the armed forces, the President is also considered the nation’s “Chief Diplomat.” In fact, given national security concerns, some defense or security related EOs (often called National Security Directives or Presidential Decision Directives) are not made public.
In addition to congressional recourse, Executive Orders can be challenged in court, usually on the grounds that the Order deviates from “congressional intent” or exceeds the President’s constitutional powers. In one such notable instance, President Harry Truman, was rebuked by the Supreme Court for overstepping the bounds of presidential authority. After World War II, Truman seized control of steel mills across the nation in an effort to settle labor disputes. In response to a challenge of this action, the Supreme Court ruled that the seizure was unconstitutional and exceeded presidential powers because neither the Constitution or any statute authorized the President to seize private businesses to settle labor disputes. For the most part, however, the Court has been fairly tolerant of wide range of executive actions.
source
http://www.thisnation.com/question/040.html
also info here - under legal conflict
https://en.wikipedia.org/wiki/Executive_order
There was ONE Executive order that congress nullified.
Congress/ House Revokes EO Jan 2, 2013
House Passes Congressional Pay Freeze, 129 Members Vote for Pay Increase
http://www.freerepublic.com/focus/f-news/2974262/posts
The House approved a bill to rescind the executive order President Obama signed last week that ended the pay freeze on federal employees, which meant that some federal workers would be getting a raise—including members of Congress. A number of lawmakers spoke out about the absurdity of the pay increase and timing of the move. Rep. Michele Bachmann said in a statement, “This executive order was not requested by Congress and we should reject it. We have a spending problem in our country and we should be looking for areas to cut spending. At a time when families across the country are cutting back we should not increase government spending and add to the debt burden by giving members of Congress a pay raise.”